Window grilles divide a single windowpane into a number of smaller panes or "lights". The grilles are made by interlocking pieces of molding in a pattern that defines a desired shape of the smaller panes. In this way, standard window sashes can be converted into a variety of different style windows including colonial, tutor, and victorian styles. For convenience, the grilles are attached on the inside of window sashes with temporary retaining devices so that the grilles can be easily removed to clean the underlying pane or to refurbish the grille.
A variety of different retaining systems have been used to attach the grilles to window sashes. Most of the systems include blades with pointed ends that are pushed into the window sashes or into glazing material sealing the panes to the sashes. The systems differ from one another by the way in which the blades are attached to ends of the grille molding.
For example, one known grille retaining system includes slots formed in the molding ends for receiving the blades. The slots permit the blades to slide back and forth along a limited length of the molding for engaging and disengaging the pointed ends of the blades with the window sash. Each of the blades includes, in addition to a blade body, a pair of tabs that are bent at right angles to the blade body against sides of the molding. The tabs guide the blade bodies along the slots and provide a grip for pushing the pointed ends of the blades into the window sash.
After the blades have been engaged with the sash a few times, holes formed by the blades in the sash become enlarged and exert less restraint on the blades. Vibrations from wind against the sashes or from opening and closing the windows can shake loose the blades from the sashes and allow the grilles to fall out of the windows. Also, when the grilles are removed from the windows, the pointed end of the blades may project from the molding ends, making the grilles dangerous to handle.
Another known grille retaining system permanently anchors the pointed end of the blades in the glazing material between the windowpane and sash. The blades are bent in the shape of a bracket having two arms. One of the arms forms a blade body and the other arm projects away from the pane. The arm that projects from the pane includes a boss that resiliently engages a notch formed in the end of the grille molding. The boss, together with the notch, functions as a detent for securing the grille to the window and for releasing the grille from the window.
However, this type of grille retaining system is known to be overly sensitive to dimensions of the grille molding. The detent arm of the blades has only a limited range of angular movement with which to engage the notches in the molding, and normal variations in the length of the molding sometimes exceeds this range. For example, if the molding is a little short, the detent arm may not engage the notch at the end of the molding with enough pressure to hold the grille in place. Adjustments are made by bending the detent arms toward or away from the window sash to match variations in the lengths of molding. These "trial and error" adjustments of each detent arm are time consuming and inconvenient.
Another known bracket for retaining window grilles includes the usual blade body that is permanently anchored in the window glazing material, but also includes a pair of resilient arms that are bent at substantially right angles from opposite sides of the blade body. Each of the resilient arms includes a boss formed on their outer surface near their end that projects from the windowpane. Slots are formed in a bottom surface of the molding adjacent to the windowpane for receiving the blade arms, and the slots are undercut along their length to capture the two bosses of each bracket between them.
Although this known retaining system allows some adjustability for engaging variable lengths of the grille molding, the slots must be formed with exceptional accuracy to maintain firm engagement with the resilient arms and to properly position the window grilles against the windowpanes. The slots are also sensitive to wear, particularly splintering at the ends of the molding, that can prevent the bosses from fully engaging the undercut portions of the slots.
The grill retaining systems that force blades between windowpanes and sashes also add a risk of damaging the windowpanes. Some of the blades are likely to engage the windowpanes by pressing against edges of the panes. Stress occurs at these points of engagement and sometimes cracks or chips the windowpanes.